Electrical conductivity,photoconductivity, and optical properties of poly(1,4‐diaminoanthraquinone) organic semiconductor for optoelectronic applications

The electrical conductivity and optical properties of the poly(1,4‐diaminoanthraquinone) [poly(1,4‐DAAQ)] have been investigated. The electrical conductivity of the polymer increases with temperature and room temperature conductivity was found to be 2.68 10^?5 S cm^?1. The optical band gap of the polymer is 1.87 eV due to the direct optical transitions. The photoconductivity of the polymer is higher than that of dark conductivity. When the light is switched on, the resistance decreases abruptly and when it is switched off, the resistance increases. This confirms that the polymer is a photoconductive material. The obtained results indicate that the poly(1,4‐DAAQ) is a photoconducting organic semiconductor with photovoltaic and dark current properties. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysis of glass transition and relaxation processes of low molecular weight polystyrene-b-polyisoprene diblock copolymers

The objective of this study is to analyze the glass transition temperature and relaxation processes of low molecular weight polystyrene-block-polyisoprene diblock copolymers with different compositions, synthesized via anionic polymerization. Thermal properties were investigated by differential scanning calorimetry and dynamic-mechanical thermal analysis, while the morphologies at room temperature were investigated by transmission electron microscopy and small-angle X-ray scattering. The χN values indicate that the diblock copolymers lie near the weak segregation regime. Three different experimental techniques were applied to determine the dynamic properties, i.e., linear viscoelastic shear oscillations, creep recovery experiments, and dielectric spectroscopy. The rheological experiments were performed above the order–disorder transition temperature where the diblock copolymers behave like a Maxwell fluid. Our results indicate that the presence of the polyisoprene segments strongly influences the monomeric friction coefficient and the tendency to form entanglements above the order–disorder temperature. Consequently, the zero-shear rate viscosity of a diblock copolymer is much lower than the zero-shear rate viscosity of the neat polystyrene block (the polystyrene precursor of the polymerization procedure). Dielectric spectroscopy enables the analysis of relaxation processes below the glass transition of the polystyrene microphase. Frequency sweeps indicate the dynamic glass transition of the polyisoprene blocks, which are partly mixed with the polystyrene blocks, which are always the majority component in the block copolymers of this study.     

Comparative Analysis and Modeling of Superoxide Dismutases (SODs) in Brachypodium distachyon L.

Superoxide dismutase (SOD, EC 1.15.1.1) is an enzyme catalyzing the dismutation of superoxide radical to hydrogen peroxide and dioxygen. To date, four types of SODs — Cu/ZnSOD, MnSOD, FeSOD, and NiSOD — have been identified. In this study, SOD proteins of Brachypodium distachyon (L.) Beauv. were screened by utilization of bioinformatics approaches. According to our results, Mn/FeSODs and Cu/ZnSODs of B. distachyon were found to be in basic and acidic character, respectively. Domain analyzes of SOD proteins revealed that iron/manganese SOD and copper/zinc SOD were within studied SOD proteins. Based on the seconder structure analyzes, Mn/FeSODs and Cu/ZnSODs of B. distachyon were found as having similar sheets, turns and coils. Although helical structures were noticed in the types of Mn/FeSODs, no the type of Cu/ZnSODs were identified having helical structures. The predicted binding sites of Fe/MnSODs and Cu/ZnSODs were confirmed for having His-His-Asp-His and His-His-His-Asp-Ser residues with different positions, respectively. The 3D structure analyzes of SODs revealed that some structural divergences were observed in patterns of SODs domains. Based on phylogenetic analysis, Mn/FeSODs were found to have similarities whereas Cu/ZnSODs were clustered independently in phylogenetic tree.     

Styrene‐vinyl pyridine diblock copolymers: Achieving high molecular weights by the combination of anionic and reversible addition–fragmentation chain transfer polymerizations

Anionic and reversible addition–fragmentation chain transfer (RAFT) polymerizations were combined for the preparation of high molecular weight (MW) amphiphilic diblock copolymers based on the hydrophobic styrene (Sty) and the more polar 2‐vinyl pyridine (2VPy) or 4‐vinyl pyridine (4VPy). In particular, four amphiphilic Sty‐VPy diblock copolymers with MWs up to 271,000 g mol^–1 were prepared. For the polymer synthesis, first, living anionic polymerization of Sty using sec‐butyl‐lithium as initiator in tetrahydrofuran at ?70 °C, followed by termination with ethylene oxide were employed for the preparation of OH‐functionalized homopolyStys. Subsequently, a modification of the OH‐terminal group was performed by the attachment of a 4‐cyanopentanoic acid dithiobenzoate chain transfer agent (CTA) group, giving a polySty macroRAFT CTA, which was extended with 2VPy or 4VPy units using RAFT polymerization. Thus, the prepared diblock copolymers comprised a first block which was near‐monodisperse in size, and a second more heterogeneous block. All diblock copolymers were characterized in terms of their MWs and compositions by gel permeation chromatography and ¹H NMR spectroscopy, respectively, giving results close to the theoretically expected values. Films cast from chloroform solutions of the diblock copolymers were investigated in terms of their bulk morphologies using transmission electron microscopy, which indicated that the minority block consistently formed the discontinuous microphase, spherical or cylindrical. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis,structure, and solvent-extraction properties of tridentate oxime ligands and their cobalt(II), nickel(II), copper(II), zinc(II) complexes

Synthesis of four different types of ligands Ar[COC(NOH)R] _n (Ar = biphenyl, n = 1, HL¹; Ar = biphenyl, n = 2, H₂L²; Ar = diphenylmethane, n = 1, HL³; Ar = diphenylmethane, n = 2, H₂L⁴; R = furfurylamine in all ligands) and their dinuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ complexes is reported herein. These compounds were characterized by elemental analysis, ICP-OES, FT-IR spectra, and magnetic susceptibility measurements. The ligands were further characterized by ¹H NMR. The results suggest that dinuclear complexes of HL¹ and HL³ have a metal to ligand mole ratio of 2: 2 and dinuclear complexes H₂L² and H₂L⁴ have a metal to ligand mole ratio of 2: 1. Square pyramidal or octahedral structures are proposed for complexes of oxime ligands. Furthermore, extraction abilities of the four ligands were also evaluated in chloroform using selected transition metal picrates such as Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺. The ligands show strong binding ability towards Hg²⁺ and Cu²⁺ ions.     

Callus induction and plant regeneration from different explants of Actinidia deliciosa

In this study, an efficient procedure was developed for callus induction and regeneration of kiwifruit (Actinidia deliciosa) using different organs of shoots developed under in vitro conditions. Effects of explants source and media (M₁, 1.0 mg l⁻¹ BA + 2.0 mg l⁻¹ 2,4-D–M₂, 1.0 mg l⁻¹ NAA + 2.0 mg l⁻¹ 2,4-D) on initiation of callus were examined in order to obtain callus for organogenesis. The best callus for plant regeneration was obtained from leaf explants on Murashige and Skoog’s medium (MS) supplemented with M₂. Formation of callus from leaf of kiwifruit (A. deliciosa) was cultured in MS medium containing different concentration of N⁶-benzylaminopurin (BA; 0.0, 1.0, 2.0, 4.0, 6.0, 8.0 mg l⁻¹) for callus proliferation and plant regeneration. Although the first shoot formation was appeared in medium containing 6.0 and 8.0 mg l⁻¹ BA, the best shoots formation was obtained in medium with 4.0 mg l⁻¹ BA.     

Fluorescent chemosensor for Ag(I) based on amplified fluorescence quenching of a new phthalocyanine bearing derivative of benzofuran

A fluorescent chemosensor for Ag(I) as a new family of peripherally functionalized zinc-phthalocyanine, 2(3),9(10),16(17),23(24)-tetrakis-{6-(-benzofuran-2-carboxylate)-hexylthio} phthalocyaninatozinc(II) {Zn[Pc(β-S(CH₂)₆OCOBz-furan)₄], (ZnPcBzF), (3), which was derivated from 6-(3,4-dicyanophenylthio)-hexyl–2-benzofuranate (BzF), (2), has been synthesized and fully characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR, MS (ESI and Maldi-TOF). An optical silver ion (Ag(I)) sensor based on the fluorescence quenching of benzofuran moiety and ZnPc core was developed. Both absorbance and fluorescence spectra of ZnPcBzF, (3) exhibit distinct changes in visible region in response to treatment with Ag(I) ion in solution. Such properties make compound ZnPcBzF, (3) intriguing candidates for incorporation into the transducer layer in optically based chemical sensors.     

Synthesis and liquid crystal properties of phthalocyanine bearing a star polytetrahydrofuran moiety

A new polymeric ligand, 6-(3,4-dicyanophenylthio)-hexyl-2-polytetrahydrofuranacetate (2) and its liquid crystalline polymeric phthalocyanine, 2,9,16,23-tetrakis-{6-(polytetrahydrofuran-2-carboxylate)-hexylthio-phthalocyaninatocobalt(II) (3), {Co[Pc(S-C₆H₁₃OCO-poly-THF)₄]}(CoPcLC) have been synthesized. The ligand and the phthalocyanine, bearing polytetrahydrofuran moieties (poly-THF), were characterized using elemental analysis, FTIR, ¹H and ¹³C NMR, and UV–Vis techniques. CoPcLC (3) promotes a greater interaction between the mesogens, resulting in solution aggregations together with a red-shift in the Q-band in the presence of the soft Ag⁺ ion. The dielectric anisotropy and phase transition temperature values of CoPcLC doped with 4-cyano-4′-n-pentylbiphenyl (5CB) were found to be 7.17 and 40.5 °C, respectively. The dielectrical anisotropy behaviour of the liquid crystals changes from the positive to the negative type. The current–voltage characteristics of the liquid crystals show a non-linear behaviour.     

A self-powered "sense-act-treat" system that is based on a biofuel cell and controlled by boolean logic

Bio-logic-al: an autonomous, integrated "sense-act-treat" system that is based on an enzymatic biofuel cell has been developed. The system couples a biocomputing logic-detection method with a drug-release system to provide a logic-activated therapeutic intervention in response to a simulated abnormal physiological state, without the need for an external power source, control electronics, or microelectromechanical actuators.     

Treatment of opium alkaloid containing wastewater in sequencing batch reactor (SBR)—Effect of gamma irradiation

Aerobic biological treatment of opium alkaloid containing wastewater as well as the effect of gamma irradiation as pre-treatment was investigated. Biodegradability of raw wastewater was assessed in aerobic batch reactors and was found highly biodegradable (83–90% degradation). The effect of irradiation (40 and 140 kGy) on biodegradability was also evaluated in terms of BOD₅/COD values and results revealed that irradiation imparted no further enhancement in the biodegradability. Despite the highly biodegradable nature of wastewater, further experiments in sequencing batch reactors (SBR) revealed that the treatment operation was not possible due to sludge settleability problem observed beyond an influent COD value of 2000 mg dm^?3. Possible reasons for this problem were investigated, and the high molecular weight, large size and aromatic structure of the organic pollutants present in wastewater was thought to contribute to poor settleability. Initial efforts to solve this problem by modifying the operational conditions, such as SRT reduction, failed. However, further operational modifications including addition of phosphate buffer cured the settleability problem and influent COD was increased up to 5000 mg dm^?3. Significant COD removal efficiencies (>70%) were obtained in both SBRs fed with original and irradiated wastewaters (by 40 kGy). However, pre-irradiated wastewater provided complete thebain removal and a better settling sludge, which was thought due to degradation of complex structure by radiation application. Degradation of the structure was observed by GC/MS analyses and enhancement in filterability tests.